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FAQ - Tarmac Repair
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A Guide to the repair of tarmac, bitmac or asphalt drives and other pavements that have been contaminated with fuel oil
Repairing fuel-damaged tarmac
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faq Overnight fuel leaked from my car, this has resulted in my tarmac drive being dissolved - it has left a couple of holes 5" wide. How can I patch these unsightly holes?
oil damaged tarmac
Tarmac is an oil-based product; the binder is a heavy tar or bitumen and as such, it can be 'thinned' by the addition of a lighter oil, such as paraffin, petrol or even turpentine.
Many automotive oils, such as petrol, diesel or even brake fluid, can 'dissolve' the binder of a tarmac and there's no way of 're-sticking' the aggregate back together. Further, the contaminating oil will seep and spread, degrading all the tarmac that it contacts. Given a few days, a petrol leak will 'eat' its way through a 75mm thick tarmac driveway; a screwdriver or stiletto heel will easily penetrate the previously 'set' surfacing and before long, the now unbound aggregate will begin to be scattered everywhere. And once a hjole appears in a tarmac surface, it just gets bigger and bigger as the edges 'crumble'.
contaminated tarmac
Contaminated tarmac showing position of cut lines at least 100mm back from damaged area
cut out contamination
Contaminated material is removed
The best remedy is to cut out the affected area to at least 100mm back from the contamination. A power saw, floor saw, angle grinder or even a hammer and bolster can be used to cut out the tarmac in a neat and tidy fashion, preferably a rectangle or octagon. The contaminated tarmac must be dug out, and the surrounding material excavated back to the cut line. All the spoil should be disposed off site, in a skip or a bin.
Most Builders' Merchants stock 25Kg bags of repair macadam, often sold under an appalling name such as 'Mac-in-a-sack' or 'Quick-Mak'. They may also sell a product known as 'Cold Pour Jointing Compound' which is used to seal the edges. For a typical residential driveway with a 75mm thick surfacing of tarmac, each 25Kg bag of repair macadam will cover approximately 0.15m² which is the equivalent of an area measuring roughly 400mm × 400mm.
The vertical edges of the hole should be primed with the Cold Pour, which may be poured on from a can or tar bucket, or 'painted' on with a brush. The hole should then be filled to about 3/4 depth with the repair macadam and compacted down with a wacker plate, small roller, a punnel or a lump hammer. A second layer should be placed immediately and again compacted so that the surface is level with the rest of the surfacing. place repair macadam
Place repair macadam
seal with cold pour
Seal top of joints
Once the hole has been filled, the joint between the repair and the existing surfacing should be sealed with more Cold Pour, capping the joint and thereby preventing water ingress. Note the comments above about how these repair macadams can remain 'sticky' for a number of weeks. Cold pour is a water-based emulsion care must be taken to avoid tracking it everywhere.
Note that Cold Pour is a jointing compound NOT a repair mastic. It should NOT be poured over fuel-contaminated tarmac in the hope of replacing the original binder and 're-setting' the aggregates. It is nasty, tacky stuff and if put it down in large areas, it will get tracked everywhere, by tyres and footwear, especially if there are light-coloured carpets in the vicinity!

As with other monolithic surfacings, tarmac cannot be 'invisibly repaired'. The patch will always look like what it is - a patch. The same applies with concrete (even the very expensive Pattern Imprinted Concrete), Resin Bonded Aggregates, Imprinted Asphalt and all other monolithic surfaces; something to bear in mind when considering specifying one of these surfacings for any project.
Although the patch will eventually become less noticeable as it 'blends in' with the rest of the pavement thanks to the effects of time and weathering, for the first few weeks, it will stand out like a black cat on a ski slope. Part of this is due to the fact that the materials differ somewhat in colour and texture, and part is due to the fact that the viewer is aware of its presence. After a couple of months, regular users of the patched pavement will no longer notice the existence of the repair, although it will still be there if you look for it. tarmac repair


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